Introduce Templates from Markus

src/nomad_simulations/schema_packages/properties/band_gap.py

@@ -4,7 +4,7 @@
 from nomad.units import ureg
 from nomad.datamodel.data import ArchiveSection
 from nomad.metainfo import MEnum, Quantity
-from nomad.metainfo.physical_properties import MaterialProperty, Energy
+from nomad.metainfo.physical_properties import DatasetTemplate, Energy
 from ..variables import (
     SpinChannel,
     MomentumTransfer,
@@ -15,15 +15,29 @@
     from structlog.stdlib import BoundLogger
 
 
-class ElectronicBandGap(ArchiveSection):  # ! TODO: add optical band gap
-    values = MaterialProperty(
-        name='BandGap',
-        fields=[Energy],
-        variables=[SpinChannel, MomentumTransfer],  # presence checked via annotations
-        iri='http://fairmat-nfdi.eu/taxonomy/ElectronicBandGap',
-        description="""Energy difference between the highest occupied electronic state and the lowest unoccupied electronic state.""",  # ? necessity
+class HomoLumoGap(ArchiveSection):  # ? class description
+    values = DatasetTemplate(
+        name='HomoLumoGap',
+        mandatory_fields=[Energy],
+        mandatory_variables=[SpinChannel],  # presence checked via annotations
+        iri='http://fairmat-nfdi.eu/taxonomy/HomoLumoGap',
+        description="""
+        The energy difference between the highest occupied spin state
+        and the lowest unoccupied spin state.
+        """,
     )
 
+    def normalize(self, archive: 'EntryArchive', logger: 'BoundLogger') -> None:
+        self.m_all_validate()  # ensure constraints 
+        if np.any(self.values.fields < 0):
+            logger.warning(f'Negative band gap detected: {self.values.fields} J')
+
+
+class ElectronicBandGap(HomoLumoGap):  # ! TODO: add optical band gap
+    values = HomoLumoGap.values.m_copy()  # ? `m_copy` supported
+    values.mandatory_variables.append(MomentumTransfer)
+    values.iri = 'http://fairmat-nfdi.eu/taxonomy/ElectronicBandGap'
+
     type = Quantity(
         type=MEnum('direct', 'indirect'),
         description="""
@@ -36,10 +50,7 @@ class ElectronicBandGap(ArchiveSection):  # ! TODO: add optical band gap
     )
 
     def normalize(self, archive: 'EntryArchive', logger: 'BoundLogger') -> None:
-        if np.any(self.values.fields < 0):  # ? check for Energy
-            logger.warning(f'Negative band gap detected: {self.values.fields} J')
-
-        if not self.variables[1]:  # ! replace with native getter
+        if not self.get_variable(MomentumTransfer).get_values():  # getter
             if self.type == 'direct':
                 self.variables.append(
                     MomentumTransfer(data=[2 * [3 * [0.0]]] * ureg.angstrom**-1)